1. Field of the Invention
The present invention relates to an optical switch employed for switching an optical path in optical communication equipment.
2. Description of the Background Art
U.S. Pat. No. 6,519,381 discloses an exemplary optical switch based on prior art. This optical switch employs a polymer optical waveguide film as a medium transferring light. In the polymer optical waveguide film formed by a polyimide film serving as the matrix, linear portions, referred to as cores, slightly higher in refractive index than the peripheral portion (clad portion) are two-dimensionally embedded and arranged in the form of a lattice. A notch is formed on the intersection between the cores. This optical switch is formed by holding the polymer optical waveguide film having the notch with keep plates having through holes corresponding to the intersection between the cores respectively to expose this intersection through the through holes respectively and arranging a driving member on each or a single surface of the intersection between the cores.
When the notch is closed in this optical switch, light is transmitted through this portion. This state is referred to as “transmissive state”. When the polymer optical waveguide film is pressed with the driving member from the backside of the notch, on the other hand, the notch is open to define a layer of air between the cores opposed to each other through the notch. If the refractive indices of the cores and the clad portion and the angle of intersection between the cores are properly set in advance, light going to pass through the optical switch is totally reflected when the notch is open to form an air layer having a sufficient thickness therein. In other words, the optical switch can switch the optical path. This state is referred to as “reflective state”.
As shown in FIG. 8 of U.S. Pat. No. 6,519,381, a plurality of cores are provided on each of input and output sides while notches are formed on respective intersections between these cores, and one of the notches intersecting with each core of the input side is in a reflective state and the other notch is in a transmissive state so that the input ports and the output ports are in one-to-one correspondence to each other. Thus, the optical switch can guide light to a desired output port.
In the optical switch disclosed in U.S. Pat. No. 6,519,381, each notch is formed with a sharp cutter or the blade of a dicer or the like. Alternatively, the notch is formed by causing cleavage while introducing the cutter or the blade.
When the notch is formed by introducing a cutter, however, chips result from this cutting, and the side surface of the cutter rubs against the workface. Thus, the side surface of the notch forming the workface is rendered irregular. In other words, the reflecting surface is rendered irregular in the reflective state. Such an irregular reflecting surface disadvantageously increases reflection loss. Also when the notch is closed to implement a transmissive state, further, the irregular side surface of the notch defines a small air gap in the notch. The small air gap reflects part of light, which in turn advances toward a reflecting port despite the transmissive state, to disadvantageously result in a crosstalk.
When the notch is formed with a dicer while rotating the blade thereof, on the other hand, the workface polished by the rotated blade exhibits a certain degree of smoothness. However, the material is partially whittled due to complete cutting, to generally result in a cut margin of about 15 μm in width. In this case, it is almost impossible to obtain a sufficiently excellent transmissive state, although a reflective state can be readily obtained.